Michael Saunders led off the ninth with a sharp single to right and advanced to second on a bunt single by Brendan Ryan. After failing to get a bunt down, Ackley earned a walk to load the bases for Jaso.
Jaso, hitting for Trayvon Robinson, worked the count full, then hit a fly ball just deep enough to left to score Saunders from third. It was Jaso's third walk-off RBI this season and team-leading 12th game-winning RBI.
"That was cool, they did all the work getting that situation on the table," Jaso said.
"He's going to stick his nose in there, he's not going to give anything away," Mariners manager Eric Wedge said. "You feel good with him up there in those situations."
The Mariners had tied the game, 2-2, in the seventh when Justin Smoak connected for a monstrous solo shot over the Mariners bullpen in left-center. Added to a double in the fifth, Smoak had his second multi-extra base hit game of the season.
The first baseman continues to make progress since being recalled from Triple-A on August 14.
"That's the ability that he has, that's the impact that he can have -- from both sides of the plate," Wedge said. "He's obviously had better ABs since he's been back here. Even that last AB, he fought all the way through it. That's what you like to see, because you're going to have more success when you have those types of ABs in the long run."
In a low-scoring affair, it was Jason Vargas who kept the Mariners in the game throughout. Despite flirting with danger on multiple occasions, the lefty allowed just two runs in 6 2/3 innings, scattering eight hits and a walk.
Vargas is 6-1 with a 1.95 ERA in his last 10 starts and has allowed just one home run in his last six outings. This comes after struggles earlier in the season when he tied a club record for home runs allowed in a month (11 in June).
"I thought he pitched a real good ballgame," Wedge said. "Not as sharp as we've seen him, but what's separated for Jason now is when he's not exactly locked in -- again, I still felt like he threw a real good ballgame -- he's still able to get people out and make pitches."
Vargas' biggest escape act came in a pivotal seventh inning, when he allowed three singles to load the bases with one out. With a pitch count already over 100 and the game tied at 1-1, Wedge left Vargas on the mound to face Joe Mauer.
The lefty-on-lefty matchup produced a groundball and a force at second, but the relay to first for the double play was too late and the Twins took a 2-1 lead. Josh Kinney came on in relief to record the final out of the inning to help limit the damage.
The seventh wasn't the only trouble Vargas ran into on Saturday. The lefty had to work from the get-go, as the Twins wasted no time scoring.
Jamey Carroll led off the game with a single, moved to second on a wild pitch and advanced to third on a groundball. After a walk to Josh Willingham, Justin Morneau hit a shallow looper to left to score Carroll.
Vargas was able to do some damage control, though, and induced an inning-ending groundout to limit the Twins to one run. The southpaw's work even gained the praise of the opposing pitcher, Scott Diamond.
"Vargas is a guy I actually watch a lot of video of to see how he handles hitters," said Diamond, who also threw 6 2/3 innings of two-run ball. "I feel like our stuff is pretty similar with the way the ball moves and how we pitch around that, too. He's having a good year and he pitched very well."
The Mariners came back with a run in the third. Saunders singled with one out and Ryan followed with a single to put runners on the corners. Ackley then singled through the right side to tie the game at 1-1, but Ryan was thrown out at third on the play to squash a further rally.
Although the Mariners had trouble throughout pushing runs across -- they left 10 on base -- they once again found a way to get the job done, improving their record since the All-Star break to 21-13.
"You could say we're starting to mesh more as a team," Jaso said. "A lot of exciting things have happened this year and I think we are kind of growing as a group. That's kind of a cool thing."